The idea that some US inhabitants deserve the land, deserve to stay and to occupy it, and that others must go – to be exterminated (Native Americans), to be exiled (black people), to be driven out (Chinese and Japanese people), to be barred from immigrating (Italians, Jews and other southern and eastern Europeans), to be removed (Mexicans) and, briefly, challenged as citizens (Irish Catholics) – has changed shape over time in terms of the permitted stayers and the non-permitted exiles.

But the conviction that only some people – that is, white people (however defined) – deserved US citizenship based on race held on for a very long time. After all, the initial US Congress began its work in 1790 by limiting eligibility for naturalisation to the free and the white.

In the 1970s, I thought changes in US laws and customs had put cries of “get out” and “go home” to rest. I thought the legislation of the 1960s on immigration, civil rights and access to the vote had put all that behind us, in law, at least, if not totally in practice. I thought the United States had turned a corner, had moved away from “this is a white man’s country” and relegated “go back to where you came from” to schoolyard taunts.

I was wrong. With so many of my compatriots, I was gravely mistaken. The past is not the past.

I also thought back then that naked voter suppression had largely ended. And yet it still exists today. But it’s not just disfranchisement that’s current. It didn’t occur to me in the 1970s that outright bigotry like Donald Trump’s would be uttered in public. It didn’t cross my mind back then that a president would indulge in textbook-level racism out loud.

Trump has made us admit that the “white man’s country” past – the past of publicly uttered white supremacy that Trump channels, the unabashed bigotry and xenophobia, the long, long past of race hate in the American south, but also in the west and the north—flourishes among us. His followers chant “send her back” and he preens in their enthusiasm.

White supremacy enjoyed a long and triumphal run, a run that continues, but the American past also includes campaigns against white supremacy, starting with anti-slavery and embodied in the black struggle for civil rights, most visible in the 1950s and 1960s but begun decades earlier and not yet ended. Black Americans led the struggle and paid the price in lives and mental health. And yet, for all that struggle and bloodshed, black Americans could not have enacted crucial legislation alone. Non-black allies also paid a price as they made the difference between an obscure struggle and widely reported campaigns. In the courts, communist allies defended black activists. In Congress, religious leaders taught representatives that black Americans, who were lifting the heaviest loads, were not in the work alone.

Just as Trump and his backers make historic racism newly visible, the American anti-racist past needs to come more fully alive. Racism may be momentarily more visible and better funded, but the 20th-century campaign for democracy is as much a part of American history. Black Americans are in the vanguard, as exemplified in the Moral Mondays campaign led by the Reverend William Barber in North Carolina – where Trump’s supporters yelled “send her back” and one of the state’s senators congratulated him on his good work. Other Americans of colour are already engaged. Progressive Democrats are joining up, as are Democrats whose constituencies are reliably Democratic. Yet among opponents of Trump’s nativism, Republicans are hardly to be found.

The notion that there are two main political parties in the US – one on the centre left, the other on the centre right – no longer holds. For the parties are increasingly defined by their racial politics. Democrats are multiracial multiculturalists. Republicans are the white party.

Even before Trump, the Republican party had been waging a southern strategy for more than half a century, ever more firmly committed to its white identity. The demography of the Republican congressional delegation, from its senators and representatives to its staffers and interns, makes a striking contrast with its Democratic counterpart. True, the Republican ranks are not 100% lily-white. But in light of Trump’s racist provocations and wide-scale Republican acquiescence, I wonder how long non-white Republicans will hold on.

Tellingly, the earliest and most emphatic Republican denunciation of Trump’s “go back” rhetoric came from Will Hurd, an African-American congressman. At this point, the Republican party seems more willing to tolerate Nazi-style racism than to denounce it unequivocally and by name.

With Trump and his party re-enacting the history of American white supremacy, citizens who cherish democracy must take the opposite side in our national drama and stage a counter re-enactment.

Just as Trump has carried his just-happen-to-be-white into proud-to-be-white followers and into white nationalism, anti-Trump Americans must carry the nation in a saner direction. And just as Trump’s racism calls up old themes in America’s history, anti-racists must now act on a history of their own, one sufficiently powerful to defeat Trumpism, as it defeated slavery, segregation and disfranchisement.

African Americans already know this history and are already motivated. Other people of colour are learning it and engaging with the cause. And while Trump has galvanised his white people for bigotry, now anti-Trump white people need to step up into activism – on behalf of multiracial, multicultural American democracy.

•Nell Irvin Painter is the author of Exodusters: Black Migration to Kansas After Reconstruction and The History of White People

• The caption to the second picture was amended on 22 July 2019 because an earlier version gave the names of those pictured in the wrong order. This has been corrected.